The sound emission of an aircraft for commercial use can reach 155 dB at takeoff, a value greater than the auditory pain threshold evaluated at 130 dB. It is therefore desirable to reduce this sound emission level. One way of attempting to solve this problem consists of absorbing the noise at one of its emission points, that is to say at the engines. Solutions have already been implemented in the “cold” parts of the engines, but the “hot” parts are currently not the subject of any acoustic treatment. It is therefore desirable to develop a material having an acoustic absorption function intended for the hot parts of aircraft engines. To do this, one way envisaged is to develop a nozzle capable of partly absorbing the noise produced inside the engine.
Furthermore, in order to fulfill a property and people protection function, the manufacture of systems capable of absorbing a lot of kinetic energy whilst having a very light weight has an undeniable advantage.
One system can satisfy these different specifications: the use of ball-based cellular materials.
However, currently there are only nickel-based spheres and ceramic or organic spheres on the market. Assembly of these elements by sintering does not allow variation to infinity of the combinations desirable for achieving the above objectives and moreover the temperature capabilities are extremely limited as regards both mechanical strength and resistance to the oxidising and corrosive environment encountered in aircraft engines.